DE102013218296B4 - Detection of crankcase intactness injuries - Google Patents

Abstract

A method for an engine, comprising: indicating degradation of the crankcase ventilation system based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking, wherein an end of the crankcase ventilation (74) is upstream of a compressor (50). is mechanically connected to an intake duct (13) of the engine.

Description

Engines may include positive crankcase ventilation systems (hereafter referred to as crankcase ventilation systems) to vent gases from the crankcase and into an engine intake manifold to provide continued evacuation of gases from within the crankcase to prevent the deterioration of various engine components in reduce the crankcase. Crankcase ventilation systems can be monitored at intervals to identify violations in the system. For example, a forced crankcase ventilation pipe may be disconnected, an oil cap may be defective, removed or loose, a dipstick may be outside, and / or other seals in the crankcase ventilation system may be broken, which can adversely affect various components trapped in the crankcase leads.

Diagnostic blow-by approaches can be used to monitor the health of a crankcase ventilation system. For example, a pressure sensor in the crankcase can be used and a valve in a PCV fresh air hose can be opened so that pressure or vacuum changes in the crankcase can be sensed to determine if there is a violation in the system. In other approaches, multiple absolute sensors, such as a barometric pressure (BP) sensor, a compressor inlet pressure sensor (CIP), a throttle inlet pressure sensor (TIP), a manifold air pressure sensor (MAP), etc., can be used in combination to determine the integrity of a crankcase - Monitor ventilation system.

An example of such a procedure is from U.S. 5,792,949 A known, with this a pressure sensor is arranged in the immediate vicinity of the PCV valve.

However, the present inventors have recognized that such approaches to such monitoring systems can add additional equipment, such as additional sensors and valves, thus adding to the cost and complexity of a crankcase ventilation monitoring system. Also, based on the location of the sensors, some combinations of pressure sensors may, under certain conditions, indicate substantially the same pressure. As a result, system redundancy occurs without any improvement in the accuracy of a diagnostic routine.

One approach to at least partially addressing these problems is to provide a method for an engine. The method includes indicating degradation of the crankcase ventilation system based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking. In this way, a system violation can be detected by an existing pressure sensor.

According to the invention, the crankcase ventilation system comprises a crankcase ventilation pipe which is coupled between an air intake duct and a crankcase. A pressure sensor (or flow sensor) is positioned within the crankcase ventilation tube to provide an estimate of the flow rate or pressure of the air flowing through the ventilation tube. During engine cranking, and while air flow through the vent tube and into the intake manifold is low, a temporary drop in pressure can be sensed by the crankcase ventilation tube pressure sensor. In response to an amplitude of the transient drop being less than a threshold value (e.g., a substantially negligible transient drop in crankcase ventilation pipe pressure), a controller may conclude that the flow through the ventilation pipe is due to a violation in the integrity of the crankcase - The ventilation system is interrupted. For example, the controller may conclude that the crankcase ventilation tube may have been disconnected.

The controller may further confirm degradation of the crankcase ventilation system based on a change in steady-state vent pressure relative to a change in steady-state manifold vacuum after engine cranking and while manifold vacuum is greater than a threshold. For example, in response to the change in steady-state air vent pressure not changing with the change in steady-state manifold vacuum, deterioration of the crankcase system can be determined and a mitigation operation can be performed. This may include the control unit setting an appropriate diagnostic code while also limiting the engine speed or load in order to delay the drainage of lubricant from the injured crankcase and the suction of lubricant from the crankcase into engine components.

In this way, by using an existing pressure sensor to identify a violation of the crankcase system, the number of sensors and valves used in a crankcase ventilation monitoring system can be reduced, providing benefits of cost and complexity reduction without the Decrease the accuracy of the impairment detection. By using different characteristics of a crankcase ventilation pressure sensor output during and after cranking to detect degradation of the crankcase system, crankcase ventilation disconnection can be diagnosed more reliably and accurately. Furthermore, the approach allows the crankcase ventilation system to remain active during a diagnostic process.

• 1 zeigt eine teilweise Motoransicht nach der Offenbarung.
• 2A bis B zeigen ein höheres Ablaufdiagramm zum Anzeigen einer Beeinträchtigung eines oder mehrerer Bestandteile eines Kurbelgehäuse-Entlüftungssystems auf der Grundlage von Veränderungen beim Kurbelgehäuse-Entlüftungsröhrendruck während des Anlassens und/oder des Motorlaufs.
• 3 bis 4 zeigen beispielhafte Verfahren zum Anzeigen einer Verletzung eines Kurbelgehäuse-Entlüftungssystems, auf der Grundlage eines vorübergehenden Abfalls beim Kurbelgehäuse-Entlüftungsröhrendruck während des Anlassens und Veränderungen beim Kurbelgehäuse-Entlüftungsröhrendruck im Verhältnis zu Veränderungen beim Krümmer-Luftdurchfluss während des Motorlaufs.
• 5 zeigt ein beispielhaftes Verfahren zum Anzeigen einer Beeinträchtigung eines PCV-Ventils auf der Grundlage von Veränderungen beim Kurbelgehäuse-Entlüftungsröhrenluftdurchfluss während des Zustandes eines geringen Krümmer-Luftdurchflusses.
• 6 zeigt ein beispielhaftes Verfahren zum Anzeigen einer Verstopfung eines Lufteinlassfilters auf der Grundlage der Ausgabe eines in dem Kurbelgehäuse-Entlüftungsrohr angeordneten Drucksensors.
• 7 bis 8 zeigen beispielhafte Veränderungen beim Kurbelgehäuse-Entlüftungsröhrendruck, die zum Anzeigen einer Kurbelgehäuseverletzung und zum Identifizieren einer Position der Verletzung verwendet werden können.
• 9 zeigt beispielhaftes Verfahren zum Anzeigen einer Luftfilterverstopfung auf der Grundlage von Veränderungen bei einem Kurbelgehäuse-Entlüftungsröhrendruck im Verhältnis zu einem sich verändernden Krümmer-Luftdurchfluss.
• 10 zeigt beispielhafte Veränderungen beim Kurbelgehäuse-Entlüftungsröhrendruck, die zum Anzeigen einer Beeinträchtigung eines PCV-Ventils verwendet werden können.

It should be understood that the summary above is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any of the disadvantages set forth above or in any part of this disclosure.

• 1 Figure 12 shows a partial engine view according to the disclosure.
• 2A 13 through B show a high level flowchart for indicating degradation of one or more components of a crankcase ventilation system based on changes in crankcase ventilation pressure during cranking and / or engine operation.
• 3 until 4th show exemplary methods of indicating a violation of a crankcase ventilation system based on a temporary drop in crankcase ventilation pressure during cranking and changes in crankcase ventilation pressure relative to changes in manifold air flow during engine operation.
• 5 Figure 12 shows an exemplary method of indicating degradation of a PCV valve based on changes in crankcase ventilation tube air flow during the low manifold air flow condition.
• 6th FIG. 10 shows an exemplary method of indicating clogging of an air intake filter based on the output of a pressure sensor located in the crankcase ventilation tube.
• 7th until 8th show exemplary changes in crankcase ventilation pressure that can be used to indicate a crankcase injury and to identify a location of the injury.
• 9 FIG. 10 shows an exemplary method of indicating air filter clogging based on changes in crankcase ventilation tube pressure relative to changing manifold air flow.
• 10 shows exemplary changes in crankcase ventilation pressure that can be used to indicate degradation of a PCV valve.

The following description relates to systems and methods for monitoring the health of a crankcase ventilation system in an engine crankcase ventilation system, such as the system of FIG 1 . The output of one or more pressure or flow sensors, such as a pressure sensor located in a crankcase ventilation pipe of the crankcase ventilation system, can be used to detect a violation of the crankcase system, a position of the injury, an impairment of a PCV valve as well as a Identify air filter clogging. An engine control unit can be configured to execute various routines, such as, for example, the routines of 2A through B and 3 through 6, to adversely affect the crankcase ventilation system based on changes in crankcase ventilation pressure (or air flow) during engine start-up and changes in crankcase ventilation pressure relative to changes in manifold air flow during engine operation to display. The crankcase ventilation tube pressure sensor can be designed to display static pressure or dynamic pressure. Further, it can be located in a venturi (a constricted portion of the vent tube) and thus sensitive to either pressure or flow rate, or both. For example, the controller may determine a violation of the crankcase system based on characteristics of a transient drop in crankcase ventilation pressure, and then further based on both the transient drops and changes in crankcase ventilation vacuum while the engine is running ( 3 , 4th , 7th and 8th ) one position and one Identify the source of the injury. As another example, the controller may determine degradation of a PCV valve based on deviations in an expected crankcase ventilation tube pressure / air flow profile relative to an actual pressure / air flow profile ( 5 and 10 ). In addition, based on deviations of a vent pressure level from a reference pressure during high manifold air flow conditions, the controller may detect air filter clogging (or inlet hose collapse), where the reference pressure (and an associated offset) during low manifold air flow conditions is in Experience is brought ( 6th and 9 ). By using the same sensor to identify a degradation in different system components, equipment reduction benefits are achieved without sacrificing detection accuracy.

With reference to 1 this now shows an exemplary system configuration of a multi-cylinder internal combustion engine, generally at 10 shown, which may be included in a drive system of a motor vehicle. The motor 10 can be at least partially controlled by a control system that includes a control device 12th includes, and input from a vehicle operator 130 via an input device 132 being controlled. In this example the input device closes 132 an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP.

The motor 10 can be a lower portion of the engine block, generally at 26th shown include that of a crankcase 28 which includes a crankshaft 30th enveloped, with an oil pan 32 is arranged below the crankshaft. An oil filler channel 29 can in the crankcase 28 be arranged so that the oil pan 32 Oil can be supplied. The oil filler channel 29 can have an oil cap 33 include to the oil duct 29 sealed when the engine is running. A level indicator tube 37 can also be in the crankcase 28 be arranged and can have a level stick 35 for measuring an oil level in the oil pan 32 lock in. In addition, the crankcase 28 several other openings for servicing components in the crankcase 28 lock in. These openings in the crankcase 28 can be kept closed while the engine is running so that a crankcase ventilation system (described below) can operate while the engine is running.

The upper section of the engine block 26th can be a combustion chamber (i.e., a cylinder) 34 lock in. The combustion chamber 34 can combustion chamber walls 36 include, being a plunger 38 is arranged in the same. The piston 38 can be attached to the crankshaft 30th be coupled so that the reciprocating movement of the piston is converted into a rotary movement of the crankshaft. The combustion chamber 34 can fuel from a fuel injector 45 (configured herein as a direct fuel injector) and intake air from an intake manifold 42 going downstream from a throttle 44 is arranged, received. The engine block 26th may also include an engine coolant temperature (ECT) sensor 46 Include that in an engine control unit 12th (described in more detail herein below).

A thrush 44 can be located in the engine intake to prevent airflow entering the intake manifold 42 enters, to control, and there can be a compressor upstream 50 go ahead, for example followed by an intercooler 52 . An air filter 54 can be upstream of the compressor 50 be arranged and can filter fresh air entering an intake duct 13th entry. The intake air can be via a cam-actuated intake valve system 40 into the combustion chamber 34 enter. In the same way, burned exhaust can be released through a cam operated exhaust valve system 41 from the combustion chamber 34 step out. In an alternative embodiment, one or more of the intake valve system and the exhaust valve system can be electrically operated.

Combustion gases pass through an upstream of a turbine 62 arranged exhaust duct 60 from the combustion chamber 34 the end. An exhaust gas sensor 64 can be upstream of the turbine 62 along the exhaust duct 60 be arranged. The turbine 62 may be equipped with a boost pressure control valve (not shown) that bypasses it. The sensor 64 a suitable sensor for providing an indication of the exhaust gas air-fuel ratio, such as a linear oxygen sensor or UEGO- (universal or widerange exhaust gas oxygen), a two-state oxygen sensor or EGO-, a HEGO (heated EGO-) , a NO _x , HC, or CO sensor. The exhaust sensors 64 can with the control unit 12th be connected.

In the example of 1 is a positive crankcase ventilation (PCV) system 16 coupled to the engine intake so that gases in the crankcase can be vented from the crankcase in a controlled manner. During no charge conditions (when the Manifold Pressure (MAP) is less than Barometric Pressure (BP), the crankcase ventilation system pulls 16 via a vent hole or crankcase ventilation pipe 74 Air in the crankcase 28 . A first page 101 the crankcase ventilation pipe 74 can be upstream of the compressor 50 mechanically with the fresh air intake duct 13th be paired or connected. In some examples, the first page 101 the crankcase ventilation pipe 74 downstream of the air filter (as shown) 54 to the intake duct 13th be coupled. In other examples, the crankcase ventilation tube may be upstream of the air filter 54 to the intake duct 13th be coupled. A second, opposite, side 102 the crankcase ventilation pipe 74 can via an oil separator 81 mechanically with the crankcase 28 be paired or connected.

The crankcase ventilation pipe 74 also includes a sensor 77 one coupled into the same to provide an estimate of that through the crankcase ventilation tube 74 provide flowing air (e.g. flow rate, pressure, etc.). In one embodiment, the crankcase ventilation tube sensor may 77 be a pressure sensor. When configured as a pressure sensor, the sensor can 77 be an absolute pressure sensor or a relative sensor. In an alternative embodiment, the sensor 77 be a flow sensor or flow meter. In yet another embodiment, the sensor 77 be configured as a venturi tube. In some embodiments, the crankcase ventilation tube can, in addition to a pressure or flow sensor 77 , optionally a Venturi tube 75 for sensing flow therethrough. In still other embodiments, the pressure sensor 77 on a neck of a venturi tube 75 be coupled to estimate a pressure drop across the venturi tube. One or more additional pressure and / or flow sensors can be coupled to the crankcase ventilation system at changing positions. For example, an air pressure sensor (BP sensor) 57 , upstream of the air filter 54 , to the intake duct 13th be coupled to provide an estimate of the air pressure. In an example where the crankcase ventilation tube sensor 77 is configured as a relative sensor, the BP sensor 57 in connection with the relative pressure sensor 77 be used. In some embodiments, a pressure sensor (not shown) can be installed in the downstream of the air filter 54 and upstream of the compressor 50 in the intake duct 13th be coupled to provide a compressor inlet pressure (CIP) estimate. Because the crankcase ventilation pipe pressure sensor 77 however, can provide an accurate estimate of compressor inlet pressure during increased engine air flow conditions (such as during engine run-up), the need for a dedicated CIP sensor may be reduced. In addition, a pressure sensor 59 downstream of the compressor 50 be coupled to provide a throttle inlet pressure (TIP) estimate. Any of the pressure sensors mentioned above can be absolute pressure sensors or relative sensors.

The PCV system 16 also vented via a line 76 (here also as PCV line 76 designated) gases from the crankcase and into the intake manifold 42 . In some examples, the PCV line 76 a one-way PCV valve 78 (i.e., a passive valve that tends to seal when flow is in the opposite direction) to allow continued evacuation of crankcase gases from inside the crankcase 28 to be assured before it comes to the intake manifold 42 is connected. In one embodiment, the PCV valve can change its flow restriction in response to the pressure drop across it (or the flow rate through it). In other examples, however, the line may 76 do not include a one-way PCV valve. In still other examples, the PCV valve can be an electronically controlled valve operated by the controller 12th is controlled. It will be appreciated that PCV flow, as used herein, refers to the flow of gases through the conduit 76 from the crankcase to the intake manifold. Similarly, PCV backflow refers to the flow of gases through the conduit 76 from the intake manifold to the crankcase. PCV backflow can occur when the intake manifold pressure is higher than the crankcase pressure (ie, while the engine is supercharged). In some examples, the PCV system 16 be equipped with a check valve to prevent PCV backflow. It will be seen that while the example shown is the PCV valve 78 shows as a passive valve, this is not to be understood as limiting and in alternative embodiments the PCV valve 78 an electronically controlled valve (e.g., a valve controlled by a powertrain control module (PCM)), where a controller can command a signal to change a position of the valve from an open position (or a position with a high flow rate) to a closed position (or a low flow position) or vice versa or any position between them.

The gases in the crankcase 28 may consist of unburned fuel, unburned air, and fully or partially burned gases. A lubricant mist can also be present. Therefore, in the crankcase ventilation system 16 different oil separators be included to reduce the leakage of oil mist from the crankcase through the PCV system. For example, the PCV line 76 a unidirectional oil separator 80 that filters oil from vapors emanating from the crankcase 28 before they go into the intake manifold 42 enter. Another oil separator 81 can be on the line 74 be arranged to remove oil from the stream of gases exiting the crankcases during supercharging operation. In addition, the PCV line 76 also a vacuum sensor coupled to the PCV system 82 lock in. In other embodiments, a MAP or a manifold vacuum (ManVac) sensor may be located in the intake manifold 42 be arranged.

The present inventors have recognized that by arranging the pressure sensor 77 in the crankcase ventilation pipe 74 a violation of the integrity of the crankcase system can be detected not only in high engine air flow conditions but also in low engine air flow conditions based on a pull down of the vacuum in the vent pipe. At the same time, the crankcase ventilation pressure sensor 77 also detect crankcase pulsations. This enables an impairment of the crankcase system to be identified more precisely, while it likewise enables a position of a damage to the crankcase system to be reliably determined. As such, since the pressure sensor in the vent tube is used to infer or estimate the presence of air flow through the vent tube, the pressure sensor can also be used (or exchanged for) as a flow meter or measuring device. Thus, in some embodiments, a violation of the crankcase system can also be identified using a flow meter or venturi in the crankcase ventilation tube. As the flow through the crankcase ventilation tube is also controlled by the opening / closing of the PCV valve 78 is affected, the same crankcase ventilation tube sensor can advantageously also be used to diagnose degradation of the PCV valve. In addition, since the crankcase ventilation pressure sensor will sense the compressor inlet pressure under engine running conditions when the engine air flow is increased, the need for a CIP sensor can be reduced. In addition, the flow through the crankcase ventilation pipe may also be affected by the clogged condition of the air filter 54 is influenced, the same crankcase ventilation tube sensor can advantageously also be used for diagnosing filter clogging. In this way, by using an existing crankcase ventilation pressure or air flow sensor of an engine system to diagnose various engine components, such as a PCV valve, an air intake filter, as well as for diagnosing a violation of the crankcase ventilation system, advantages of hardware - and software reduction in the engine system can be achieved.

The control unit 12th is in 1 shown as a microcomputer incorporating a microprocessor unit 108 , Input / output ports 110 , an electronic storage medium for executable programs and calibration values, in this particular example as a read-only memory chip 112 shown random access memory 114 , battery-powered storage 116 and includes a data bus. The control unit 12th can send different signals from to the engine 10 coupled sensors, including the measurement of the intake air mass flow ("MAF") from "an air mass flow sensor 58 , the engine coolant temperature ("ECT") from the temperature sensor 46 , the PCV pressure from the vacuum sensor 82 , the exhaust air-fuel ratio from the exhaust gas sensor 64 , the crankcase ventilation pressure sensor 77 , the BP sensor 57 , the CIP sensor 58 , the TIP sensor 59 etc. Furthermore, the control unit 12th monitor and adjust the position of various actuators based on input received from the various sensors. These actuators can, for example, be the throttle 44 who have favourited Inlet and Outlet Valve Systems 40 , 41 and the PCV valve 78 lock in. The permanent storage 112 of the storage medium can be programmed with computer readable data representing instructions issued by the processor 108 can be carried out to carry out the methods described below, as well as other variations that are contemplated but not specifically listed. Exemplary methods and routines are described herein with reference to FIG 2A until 6th described.

In this way, the system of 1 various methods of diagnosing engine components coupled to a crankcase ventilation system based on at least one estimated crankcase ventilation tube pressure. In one embodiment, a method is provided for an engine that includes indicating impairment of the crankcase ventilation system based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking. In another embodiment, an engine method is enabled which enables a location of a violation of the crankcase ventilation system to be indicated based on both a temporary drop in crankcase ventilation pressure during cranking as well as a change in crankcase ventilation pressure during steady-state engine air flow. In yet another embodiment, an engine method is enabled that includes, during engine cranking while manifold air flow is less than a threshold, increasing the throttle opening and adversely affecting the crankcase ventilation system based on a change in crankcase ventilation tube pressure thereafter display the throttle opening. In yet another embodiment, a method is provided for an engine that includes indicating impairment of the intake air filter based on a pressure sensor in a crankcase ventilation tube. In another embodiment, a method is provided for an engine that enables an impairment of a valve coupled between a crankcase and an intake manifold to be indicated based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking.

Now 2A facing up to B is a procedure 200 to indicate impairment of one or more engine components, including crankcase ventilation system components and intake air filters, based on changes in crankcase ventilation pressure (or air flow) during engine startup and operation. Using the same sensor to detect impairment in multiple engine components provides cost and component reduction benefits.

at 202 an engine start from standstill can be confirmed. For example, it can be confirmed that the engine has been completely stopped for a period of time and the engine is started from the completely stopped state. After confirmation, at 204 the engine can be started by starting the engine with the assistance of a starter motor. Next can be at 206 determine whether the intake manifold vacuum is greater than a threshold. If not, can 208 an actuator can be adjusted to increase the intake manifold vacuum up to the threshold. In one example, the actuator being adjusted may be an intake throttle, the adjusting including increasing an opening of the throttle. In another example, the actuator that is adjusted may be a PCV valve coupled between the crankcase and the intake manifold, the adjustment opening the PCV valve (if the valve is a switching valve) or increasing an opening of the PCV valve. Valve (if the valve is a duty cycle controlled valve).

As such, the PCV valve can respond to both the pressure drop across it and the rate of flow of air through it. Specifically, when in a low throttling position, the rate of flow through the crankcase ventilation tube ("CVT") is high. In comparison, when it is in the high throttling position (sound-limited volume flow), the flow rate through the CVT is fixed (neglecting the relatively small blow-through component at a high ManVac). When the manifold vacuum becomes substantially enough to drive flow (e.g., 5 kPa) but not high enough to start causing throttling in the PCV valve (e.g. 25 kPa), a very high CVT flow rate occurs on. This high flow rate can be seen as a pressure drop in the CVT pressure sensor. The presence of this debris confirms proper PCV operation and the absence of a crankcase injury.

Once the intake manifold vacuum is at the threshold of 206 until 208 the routine continues 210 wherein, while the engine is being started and while the vacuum is maintained at or above the threshold vacuum level, monitoring a crankcase ventilation tube pressure (and / or air flow). This includes monitoring an output from the crankcase ventilation pressure sensor during engine cranking, while engine speed is below a threshold speed and before fuel is injected into any cylinder.

As such, during engine cranking, the intake manifold vacuum may be low such that the position of the PCV valve of the crankcase ventilation system is open (e.g., the PCV valve may be fully open or in a position with maximum effective area). This causes a large flow of air to be drawn through the intake air filter, then through the crankcase ventilation pipe, then through the crankcase, into the intake manifold. This flow through the crankcase ventilation pipe to the intake manifold can be measured by a flow meter or venturi tube as a temporary increase in air flow at the crankcase ventilation tube or by a pressure sensor as a temporary decrease in crankcase ventilation pressure (or a temporary increase in the crankcase) Ventilation pipe negative pressure) can be recorded. As engine speed increases and manifold vacuum increases subsequent to cranking, air flow through the crankcase ventilation tube into the intake manifold may decrease. Consequently, the Routine at 212 includes assessing characteristics of a transient drop in crankcase ventilation pressure during cranking. The estimated properties include, for example, an amplitude of the temporary drop, a time point of the drop (e.g., with respect to engine speed or piston position), a duration of the drop, and so on.

The routine closes next 214 determining and indicating a degradation of the crankcase ventilation system based on one or more characteristics of the transient drop in crankcase ventilation pressure during engine start-up. As discussed above, during engine cranking, when the manifold vacuum is lower, there is increased air flow from the air filter through the crankcase ventilation tube to the intake manifold as a temporary drop in crankcase ventilation pressure (or a temporary increase in ventilation ventilation) recognize. However, this temporary drop can be affected by the presence of an injury to the crankcase system (e.g. if the vent pipe is disconnected) as well as the position of the PCV valve (e.g. the PCV valve is stuck open or stuck closed). As a result, as with 3 until 4th In more detail, a violation of the integrity of the crankcase ventilation system and a position of the violation can be displayed based on at least one amplitude of the temporary drop in the crankcase ventilation pipe pressure. For example, in response to the transient decay amplitude being less than a threshold during cranking, a violation of the crankcase system may be determined.

Subsequent to the detection of a violation of the crankcase system, the routine continues to 216 and a degradation of the PCV valve is determined based on the characteristics of the transient pressure change across the crankcase ventilation tube. As in 5 Specifically, this includes indicating PCV valve degradation based on an estimated crankcase ventilation pressure profile that deviates from an expected profile during engine cranking. It will be appreciated that while the routine shows that PCV valve degradation is determined after a crankcase system injury is diagnosed, in alternative embodiments the diagnoses may be performed in parallel.

After diagnosing a violation of the crankcase system and degradation of the PCV valve during engine cranking, the routine closes 218 injecting fuel into the engine cylinders and initiating a first cylinder combustion event. During engine cranking, the intake manifold air flow may be lower, and as the engine speed increases (eg, up to an idle speed), the intake manifold air flow may gradually increase. Thereafter, the control unit can continue the cylinder combustion events to enable the engine to run up. at 220 it can be confirmed that the intake manifold air flow (or engine intake air flow) is higher than a threshold air flow. As such, once the engine is at or above idle speed, manifold air flow and crankcase ventilation tube pressure may be at steady state levels. Specifically, the engine speed (together with the throttle position) influences the intake manifold pump-out characteristics during cranking and run-up, which influences a PCV valve position.

at 222 the routine includes monitoring steady-state manifold air flow and steady-state crankcase ventilation pressure. After that, at 224 and 226 , the routine includes determining deterioration in the crankcase ventilation system and deterioration in an intake air filter based on the estimated change in crankcase ventilation tube pressure under steady state conditions. As in 3 until 4th elaborated, this includes 224 , indicating a deterioration in the crankcase system based on a change (e.g., decrease) in steady-state crankcase ventilation pressure relative to a change (e.g., increase) in steady-state manifold air flow during engine operation. As in 5 explained in more detail, includes the display of an impairment of the air filter 226 , indicating a degree of air filter clogging based on a rate of change (eg, a rate of decrease) in steady-state crankcase ventilation pressure while the engine is running. As detailed herein, air filter clogging / hose collapse detection is performed while the engine is running because the diagnosis is more sensitive at higher engine air flow rates. It will be appreciated that while the routine shows the air filter degradation is being determined in parallel with diagnosing a crankcase system injury, in alternative embodiments the diagnoses may be performed sequentially.

at 228 After all diagnostic routines have been performed, one or more diagnostic codes can be set to indicate a deterioration in the affected engine component. As such, different diagnostic codes can be set to indicate air filter clogging, crankcase system violation (including different codes to indicate the location / nature of the violation), and PCV valve degradation. at 230 the routine includes taking mitigation action based on the indication and the diagnostic code that was set.

In one example, the controller may also record a number of crankcase injury detections to determine whether a threshold number of injury detections has been met. For example, the diagnostic routines of 2A through B are repeated multiple times during a given engine operation, including repeating them continuously from key-on to key-off as well as during key-off. If the routine indicates a crankcase injury, the controller may record each instance of an injury detection for that engine operating time and execute a notification routine once a threshold number of detections has been reached. In some embodiments, the threshold may be an injury detection. In other embodiments, to avoid false positives, the threshold may be multiple violation detections such as two, five, ten, and so on. As soon as the threshold number of injury detections is reached, a message can be displayed for the vehicle driver, for example by activating a malfunction indication light (MIL) in order to inform the driver of the vehicle about the detected crankcase injury. In addition, the operator can be asked to check for possible injury positions (e.g. a loose or missing oil cover or an incorrectly aligned / loose dipstick). Alternatively, the likely location of an injury (as in 4th determined, detailed below).

The mitigation actions may also include adjusting one or more operating parameters to prevent additional engine damage during engine operation with an injured crankcase, PCV valve, or clogged filter. For example, mitigation actions may include acting to delay drainage of lubricant from the crankcase if the crankcase is indicated to be damaged. Other exemplary mitigation actions include decreasing intake of air into the engine, limiting engine speed or torque, limiting amount of fuel injected to the engine, limiting throttle opening, limiting amount of boost, turning off the turbocharger and / or take various other acts designed to limit aspiration of engine lubricant from the injured crankcase. In some embodiments, the mitigation action taken may be one of several mitigation actions taken when a crankcase injury is detected. As yet another example, the multiple mitigation acts may include adding lubricant to the crankcase or pumping lubricant from a secondary reservoir and into the crankcase.

In one example, in response to the crankcase ventilation pipe being disconnected, supercharged engine operation (i.e., where MAP> BP) may be limited or suspended. In another example, in response to an oil cap loosening or an oil dipstick going out of position, an engine speed may be limited. Limiting an engine speed can reduce oil slingshots, because at high engine speeds it is more likely that centrifugal oil will leak through the oil cap / dipstick than at low engine speeds. As yet another example, no failure mode action may be taken in response to a PVC valve stuck closed since the blow-by gas (and any entrained oil mist) is simply directed to the compressor inlet and then burned. In an alternate example, in response to an indication that the crankcase ventilation tube is disconnected, a controller may limit engine speed to a greater extent, while limiting engine speed to a lesser extent in response to an indication of PCV valve degradation.

Now 3 turned towards a procedure 300 for indicating degradation of the crankcase ventilation system based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking. The method also enables degradation of the crankcase ventilation system to be determined based on a change in crankcase ventilation tube pressure relative to a change in manifold air flow during engine running conditions.

The routine of 3 works on the principle that if the drop occurs (that is, if there is high CVT flow while a PCV valve is in a low restriction position) then the integrity of the PCV system can be confirmed ( with the exception of a separation on the first page 101 ). A separation on the first page 101 can be easily detected in vehicles equipped with a MAF sensor. For vehicles without MAF sensors, the separation is on the first side 101 detectable by the lack of a high engine air flow pressure drop across the MAF sensor 58 or the CVT pressure sensor 77 .

at 302 the routine includes estimating a crankcase ventilation tube pressure during engine cranking and monitoring a temporary drop in crankcase ventilation tube pressure during engine cranking. The crankcase ventilation tube pressure can be estimated or inferred by one of a pressure sensor, a flow sensor, or a venturi tube coupled into the crankcase ventilation tube. As used herein, estimating crankcase ventilation pressure during engine cranking includes prior to a first stationary combustion event, that is, prior to fuel injection to any engine cylinder. When the flow rate through the CVT is low, the CVT pressure sensor is basically a static pressure sensor. It records both the permanent drop in flow pressure due to the flow through the air filter and the crankcase pressure pulsations. Pipe disconnections and crankcase injuries affect the pulsation amplitude. at 304 For example, an amplitude of the transient decay can be determined and compared in relation to a threshold amplitude. In one example, the threshold amplitude may be based on manifold vacuum during engine cranking. The threshold value can be increased here if the expected flow rate through the PCV valve changes. That is, under some conditions the threshold amplitude can increase with increasing manifold vacuum, and under other conditions the threshold amplitude can decrease with increasing manifold vacuum.

If the transient decay amplitude is less than the threshold, then the routine finishes 314 detects and displays a deterioration in the crankcase ventilation system. That is, a system violation may be detected in response to insufficient air flow through the crankcase ventilation tube during cranking. Indicating a degradation in the crankcase ventilation system includes indicating that the crankcase ventilation tube is disconnected. For example, the crankcase ventilation pipe may be on a first side, where the ventilation pipe is mechanically coupled to the air intake duct (upstream of a compressor), or on a second, opposite, side where the ventilation pipe is mechanically coupled to the engine crankcase via an oil separator, have been separated. As in 4th Specifically, the controller may be configured to perform an additional routine to perform based on both the temporary drop in crankcase ventilation tube pressure during engine cranking (when an engine air flow rate is lower) and a change in steady-state crankcase ventilation tube pressure Relate to a steady state change in manifold air flow during engine running conditions (when the engine air flow is higher) to identify the location and nature of the injury (e.g., the location of the separation of the vent). In this manner, a controller can indicate disconnection of a crankcase ventilation tube from a crankcase ventilation system based on changes in air flow through the crankcase ventilation tube during engine cranking and running.

to 304 returning, if the amplitude of the transient decay is not less than the threshold, it may be possible that there is no violation of the crankcase system. To confirm this, the routine continues to determine a violation of the crankcase system during engine running conditions. In detail, at 306 It can be confirmed that the manifold vacuum is higher than a threshold value. That is, it can be confirmed that the engine has passed the engine cranking condition and is running at or above a defined engine speed (e.g., at or above an engine idle speed) when the engine air flow rate (inferred or measured) is higher. After confirming that the manifold air flow is greater than the threshold, the routine includes, at 308, monitoring a change in steady state crankcase ventilation pressure relative to a change in steady state manifold air flow. Specifically, as the engine is running and the engine speed increases, the steady-state manifold air flow may gradually increase. At the same time, in the absence of any injury, the crankcase ventilation pressure can be expected to gradually decrease (that is, an amount of negative pressure created in the crankcase ventilation can be increased due to increased air flow through the crankcase ventilation).

at 310 For example, while the engine is running, it can be determined whether the decrease in steady-state crankcase ventilation (CVT) pressure is proportional to the increase in steady-state manifold air flow. That is, it can be determined whether there is more than a threshold amount of negative pressure created at the crankcase ventilation tube during engine operation with high engine air flow. If, during engine operation, the change in steady-state crankcase ventilation pressure and steady-state manifold air flow is proportional, then it can be determined at 312 that there is no degradation or violation of the crankcase ventilation system. If the change is not proportional, then the routine continues 314 to degrade the crankcase ventilation system (e.g., that the Crankcase ventilation pipe is disconnected). For example, in response to decreased or no vacuum generation in the crankcase ventilation tube at higher engine air flows, a crankcase injury is determined. As used herein, determining whether, while the engine is running, the decrease in steady-state crankcase ventilation tube pressure (CVT) is proportional to the increase in steady-state manifold air flow can determine whether their ratio deviates from a threshold ratio or whether their absolute difference is greater is as a threshold difference.

A control unit can be used with 314 indicate the violation of the crankcase ventilation system by setting a diagnostic code. Furthermore, one or more mitigation actions can be carried out in response to the notification. These may include, for example, limiting engine speed and load so as to reduce / delay the drainage of lubricant from the injured crankcase and the drawing of lubricant from the crankcase into engine components. Exemplary images used to identify a violation of the crankcase system are attached herein 7th until 8th illustrated.

Now 4th facing, illustrates the procedure 400 a routine that can be executed to determine a location of a crankcase system injury based on both a temporary drop in crankcase ventilation pressure during engine cranking and a change in crankcase ventilation tube vacuum during engine startup and after.

at 402 It can be confirmed that the amplitude of the transient drop in crankcase ventilation pressure at cranking is less than a threshold value. As in 3 Specifically, during engine cranking, when the engine air flow is lower (in the absence of injury), a higher air flow through the crankcase ventilation tube can be sensed, which is indicated by the crankcase ventilation tube pressure sensor as a temporary drop (or increase) in the ventilation tube pressure at the vent tube negative pressure) is detected. If there is an injury, an amplitude of the transient fall may be decreased.

After confirmation, at 404 determine whether a ratio of the decrease in steady-state crankcase ventilation tube pressure (CVT) while the engine is running (that is, after the engine is started, while the engine speed is greater than a threshold value) to the increase in steady-state manifold air flow while the engine is running is less than is a threshold ratio. Alternatively, it can be determined whether the absolute difference between them is greater than a threshold difference. Therefore, it can be determined whether vacuum generation at the vent pipe is at or above a threshold level during higher engine air flows.

In yet another embodiment, if a temporary drop is observed, it can be determined that the PCV system has not degraded and the controller can then refer to a disconnect on the first side 101 check. This can be done by looking for an incorrect MAF reading and a pressure drop on the MAP sensor that is too small at high engine air flow rates. Alternatively, the disconnection on the first side may be identified based on a pressure drop across the CVT pressure sensor 77 is too small at high engine air flow rates. The detection of pulsations on the CVT pressure sensor 77 can also be used.

In response to the transient drop in crankcase ventilation pressure during cranking being less than a threshold amplitude and the decrease in steady-state crankcase ventilation pressure during the increase in steady-state manifold air flow is less than a threshold rate while the engine is running, a violation of the crankcase ventilation system on a first side of the crankcase ventilation tube may be determined at 406. Further, in response to a muffled transient drop in crankcase ventilation vacuum during engine start-up and the fact that essentially no crankcase ventilation vacuum (zero) is generated during engine start-up, it will be determined that the violation of the crankcase ventilation system was due to this is that the crankcase ventilation pipe is separated on the first side where it is mechanically connected to an air intake duct. Exemplary images used to identify a first side crankcase system injury are attached herein 7th illustrated.

In comparison, in response to the transient drop in crankcase ventilation pressure during cranking being lower than a threshold amplitude and the decrease in steady-state crankcase ventilation pressure during the increase in steady-state manifold air flow during engine operation may be higher than a threshold rate , at 408 a violation of the crankcase ventilation system is detected on a second side of the crankcase ventilation duct. For example, in response to a muffled transient drop in crankcase ventilation tube vacuum during engine cranking and to a reduced crankcase ventilation tube vacuum being created during engine start-up, an injury on the second side of the ventilation tube is detected. In particular, it can be determined that there is an injury to the crankcase system on a second, opposite, side of the crankcase ventilation tube where it is mechanically connected to the crankcase. As such, an injury to the crankcase system on the second side can include a separation of the crankcase ventilation pipe from the crankcase on the second side, a loosening of a crankcase oil filler opening cover, a loosening of a crankcase oil level stick and a blockage of the crankcase ventilation pipe on the second Include page.

In order to distinguish between the different injuries to the second side crankcase system, the routine then proceeds to 410, wherein an opening size of the injury is determined. In one example, an opening size of the injury can also be determined. at 412 it can be determined whether the opening size is larger than a threshold size. If so, then at 414 based on the opening size being larger than the threshold value, a loosening of the crankcase oil filler cap can be determined. Otherwise at 416 It can be determined that the injury on the second side is due to a separation of the crankcase ventilation pipe from the crankcase on the second side, a loosening of the crankcase oil level stick or a blockage of the crankcase ventilation pipe on the second side. Exemplary images used to identify an injury to the crankcase system on the second side are attached herein 7th until 8th illustrated.

As such, when the PCV valve is in the low restriction (fully open) position, there are typically large air flows in the crankcase ventilation tube. The PCV valve may be in this position due to standard pneumatic control, active PCM control, or a PCV valve malfunction. This high air flow rate is to be sensed as a decrease in pressure or an increase in flow rate at the crankcase ventilation tube pressure / flow rate sensor. In one example, manifold vacuum can be calculated and used to infer PCV valve position. If the crankcase is damaged (cover removed, dipstick out of position, or crankcase ventilation pipe disconnected), the high air flow rate while the PCV valve is open cannot be detected. For example, the pressure drop does not occur or is noticeably reduced. The amplitude of the pressure drop, or the magnitude of the crankcase ventilation tube air flow rate, also goes down as the area (opening area or opening size) of the lesion increases. Loss of oil cap and hose disconnection will likely lift the waste entirely. Some reduced drop can also occur with a dipstick out of position.

After determining a location and nature of a violation of the crankcase system at 406, 414 and 416 the routine advances 418 to display the location and nature of the violation of the crankcase system by setting a diagnostic code. As such, a different diagnosis code may be set based on whether a violation is detected on the first side or the second side of the crankcase ventilation tube and also based on the nature of the injury on the second side. at 420 A MIL can be illuminated and / or a notification can be placed to inform the driver of the nature and location of the violation To teach crankcase system. at 422 One or more engine operating parameters can be adjusted to temporarily limit engine performance to reduce lubricant leakage from the injured crankcase ventilation system and ingestion of lubricant into engine components (which can degrade engine operation).

As such, if the crankcase ventilation tube is disconnected on the main engine air line (i.e., at the compressor inlet, also referred to herein as the first side), the high air flow rate while the PCV valve is fully open will still be detectable . In one example, an engine control system may limit engine charging in response to an indication of an injury located on the first side of the crankcase ventilation tube or an injury located on the second side of the crankcase ventilation tube. For example, engine operation can be interrupted while charging.

Now 7th facing, is at the , and an exemplary injury diagnosis of the integrity of the crankcase system is shown. In detail, they show until Characteristics of a temporary drop in crankcase ventilation tube (CVT) pressure during cranking in the respective upper diagrams (the diagrams 702 , 712 , 722 ) and characteristics of a decrease in crankcase ventilation pipe pressure with increasing manifold air flow while the engine is running (steady state conditions) in the respective lower graphs (the graphs 704 , 714 , 724 ). The upper graphs of the figures are plotted against time of engine operation, while the lower graphs of the figures are plotted against engine air flow rate (as shown) along the x-axis.

As previously detailed, the location of the crankcase ventilation duct installation, as well as the specific location of the crankcase ventilation duct sensor within the duct, cause the crankcase ventilation duct to vacuum at high engine air flow rates. Thus, if the sensor detects the negative pressure, it can be determined that there is no injury and that the vent tube is properly attached. However, if the negative pressure is not detected, a violation of the intactness of the crankcase system is detected. As such, separation of the vent pipe on one side (on a first side where it connects to the air intake duct or a second side where it connects to the crankcase) can result in reduced negative pressure at high engine air flow rates (where the degree of vacuum reduction differs based on whether the injury is on the first or second side). In addition, when it is separated on the second side, crankcase pulsations cannot be sensed.

the shows a first example, where the amplitude of the temporary drop in CVT pressure (diagram 702 ) is greater than a threshold level, indicating adequate air flow through the crankcase ventilation tube during engine cranking. In addition, while the engine is running, a decrease in steady-state CVT pressure is proportional to an increase in steady-state manifold air flow (Graph 704 ). In other words, as engine air flow increases, there is a smaller but gradual flow through the vent tube and a corresponding negative pressure is created and sensed by a pressure or flow sensor in the crankcase ventilation tube.

the shows a second example, where the amplitude of the transient drop in CVT pressure (diagram 712 ) is less than the threshold level, indicating insufficient air flow through the crankcase ventilation tube during engine start-up. In addition, while the engine is running, a decrease in steady-state CVT pressure is not proportional to an increase in steady-state manifold air flow, but the decrease is even greater than a threshold rate (Graph 714 ). Specifically, during high engine air flow conditions (compared to the negative pressure generated in the absence of injury, as in diagram 704 shown) a reduced negative pressure sensed by a pressure or flow sensor in the crankcase ventilation tube. Herein, in response to the transient drop in crankcase ventilation pressure being less than the threshold amplitude and the decrease in crankcase ventilation pressure during the increase in sustained manifold air flow being greater than the threshold rate, a violation of the crankcase ventilation system at the second side of the crankcase ventilation tube is displayed. The second side corresponds to a side where the crankcase ventilation tube is mechanically coupled to the crankcase. As in 8th Further, on the basis of the properties of the crankcase ventilation pipe pressure and flow rate, various injuries to the crankcase system can be distinguished.

the shows a third example, where the amplitude of the temporary drop in CVT pressure (diagram 722 ) smaller than the threshold dimension (in the example shown, smaller than the amplitude of the diagram 702 , but larger than the amplitude of the diagram 712 ), which indicates insufficient air flow through the crankcase ventilation tube during engine start-up. In addition, while the engine is running, a decrease in steady-state CVT pressure is not proportional to an increase in steady-state manifold air flow (Graph 724 ). Specifically, during high engine air flow conditions (compared to the negative pressure generated in the absence of injury, as in diagram 704 shown) essentially no negative pressure (zero negative pressure) sensed by a pressure or flow sensor in the crankcase ventilation tube. Herein, in response to the transient drop in crankcase ventilation pressure being less than the threshold amplitude and the decrease in crankcase ventilation pressure during steady-state increase in manifold air flow being less than the threshold rate, a violation of the crankcase ventilation system at the displayed on the first page of the crankcase ventilation tube. The first side corresponds to a side where the crankcase ventilation pipe is mechanically coupled to the air intake duct. For example, it may be indicated that the injury on the first side is due to the crankcase ventilation duct being disconnected from the air intake duct on the first side.

Now 8th facing, is at the , and An exemplary injury diagnosis of the integrity of the crankcase system is shown to distinguish between different conditions that may result in an injury identified on the second side of the crankcase ventilation tube. In detail, they show until Characteristics of a temporary drop in crankcase ventilation tube (CVT) pressure during cranking in the respective upper diagrams (the diagrams 802 , 812 , 822 ) and characteristics of a decrease in crankcase ventilation pipe pressure with increasing manifold air flow while the engine is running (steady state conditions) in the respective lower graphs (the graphs 804 , 814 , 824 ). All of the upper diagrams are plotted against the time of engine operation along the x-axis, while all lower plots are plotted against the engine air flow rates along the x-axis.

the Figure 13 shows a first example of a crankcase system injury on the second side of the crankcase ventilation tube, caused by a crankcase oil fill port cover coming off. Herein is an amplitude of the temporary drop in CVT pressure (Diagram 802 ) less than the threshold level, indicating insufficient air flow through the crankcase ventilation tube during engine cranking. In addition, while the engine is running, a decrease in steady-state CVT pressure is not proportional to an increase in steady-state manifold air flow. In detail, according to a threshold level of the engine air flow (diagram 804 ) no negative pressure sensed by a pressure or flow sensor in the crankcase ventilation tube. Here, further based on that an opening size of the lesion is larger than a threshold amount, a condition of an oil cap missing is displayed.

the Figure 12 shows a second example of a crankcase system injury on the second side of the crankcase ventilation tube caused by a crankcase oil level stick being misaligned. Herein is an amplitude of the temporary drop in CVT pressure (Diagram 812 ) less than the threshold level, indicating insufficient air flow through the crankcase ventilation tube during engine cranking. In addition, while the engine is running, a decrease in steady-state CVT pressure is not proportional to an increase in steady-state manifold air flow (Graph 814 ). In particular, no negative pressure is sensed by a pressure or flow sensor in the crankcase ventilation tube during high engine air flow conditions. Here, further based on the fact that an opening size of the injury is smaller than a threshold level, a state of a missing gauge is displayed.

It will be appreciated that in embodiments where the crankcase ventilation tube includes a venturi with an coupled pressure sensor, in response to an oil cap loosening or a dipstick out of position, the coupled pressure sensor causes a large one resulting air flow through the venturi tube can be sensed as a deep negative pressure. As such, the negative pressure generated due to the fact that an oil cap comes loose can be greater than the negative pressure generated due to the fact that the level stick is out of position.

the Figure 12 shows a third example of a crankcase system injury on the second side of the crankcase ventilation tube caused by the crankcase ventilation tube being blocked or clogged on the second side. Herein is an amplitude of the temporary drop in the CVT Pressure (diagram 822 ) less than the threshold level, indicating insufficient air flow through the crankcase ventilation tube during engine cranking. In addition, while the engine is running, an increase in steady-state CVT pressure is observed while an increase in steady-state manifold air flow is observed. Specifically, during high engine air flow conditions, a high (positive) pressure is sensed by a pressure or flow sensor in the crankcase ventilation tube. In response to these conditions, a clogging of the crankcase ventilation pipe on the second side (which is coupled to the crankcase is detected.

In this way, an existing sensor used to monitor the crankcase ventilation system can also be used to reliably identify a position and nature of a violation of the integrity of the crankcase system.

Now 5 facing, is an exemplary procedure 500 for indicating degradation of a PCV valve (i.e., a valve coupled into a crankcase ventilation line between a crankcase and an intake manifold) based on changes in crankcase ventilation pressure and / or air flow rate during engine start-up. In itself, the routine of 5 after confirming whether crankcase damage has been determined based on characteristics of the temporary waste, are executed.

In itself, the process is valued by 5 the PCV flow characteristics while the engine is running (or during a maintenance operation), provided that both the pressure drop across the PCV valve (ManVac) and the flow rate through the valve (CVT flow rate) are measured by the CVT pressure sensor. In some embodiments of 5 the method can easily verify the CVT flow rates at given ManVacs. Therein, at the most constrained PCV valve position, the CVT flow rate will be essentially low so it will be in the noise. At the position with the least restricted flow rate, the flow rate will be significant (i.e. there will be a temporary drop).

at 502 the routine includes confirming that the engine intake air flow rate is less than a threshold flow rate. In one example, the engine intake air flow rate may be lower than the threshold flow rate during engine cranking and early startup when the engine speed is slower than a threshold speed and before a threshold number of combustion events has occurred. Next, at 504, it may be confirmed that the manifold vacuum is lower than a threshold vacuum level. For example, it can be confirmed that the manifold negative pressure is lower than 40 kPa. If the manifold vacuum is not less than the threshold, then at 505 an actuator can be adjusted to ensure a desired manifold vacuum level. For example, a throttle opening can be adjusted so as to keep manifold vacuum below the threshold vacuum level. As such, since the throttle opening is linked to a flow rate through a PCV valve, the throttle opening can be adjusted to ensure a manifold vacuum level (e.g. 13 kPa) so that maximum flow through the PCV valve is guaranteed.

The routine of 5 uses the output of a crankcase ventilation pressure sensor to estimate degradation of the PCV valve. In particular, a relative sensor in the crankcase ventilation tube can advantageously be used as a flow meter to sense changes in the air flow rate in the crankcase ventilation tube. However, such a pressure sensor can correlate any negative pressure in the crankcase ventilation tube as a flow rate. In other words, a flow through the crankcase ventilation pipe can be sensed as a negative pressure on the crankcase ventilation pipe pressure sensor, and likewise a negative pressure in the crankcase ventilation pipe can be sensed as a negative pressure on the crankcase ventilation pipe pressure sensor. Thus, by performing the diagnostic routine when the engine intake air flow rate is lower than a threshold flow rate, only during conditions when the engine intake air flow rate itself does not cause negative pressure to be sensed is set to an output of a crankcase ventilation tube pressure sensor. Likewise, by performing the diagnostic routine when a manifold vacuum is less than a threshold vacuum level, only during conditions when the manifold vacuum itself does not cause a vacuum to be sensed is placed on an output of a crankcase ventilation pressure sensor. In addition, during conditions when engine intake air flow is low and manifold vacuum is low (i.e., during engine cranking and early start-up), an air flow rate through the crankcase ventilation tube is expected to be high. Thus, by running the diagnostics during these conditions, PCV valve diagnostics based on changes in crankcase ventilation tube air flow will be only possible if there is sufficient air flow through the vent tube for a reliable diagnosis.

at 506 The routine includes determining an expected crankcase ventilation tube pressure and / or air flow profile based on the current engine intake air flow and manifold vacuum levels. The expected profiles may include an expected vent pipe pressure and an expected vent pipe flow rate for a given engine speed. at 508 the routine includes estimating an actual crankcase ventilation tube pressure and / or air flow profile based on the output of the crankcase ventilation tube pressure sensor. It will be appreciated that in alternative embodiments, the estimated profile may be based on the output of a dedicated crankcase ventilation tube flow sensor or a pressure sensor coupled to the neck of a crankcase ventilation venturi tube. The estimated profiles may include measured and / or inferred vent pipe pressure and measured and / or inferred vent pipe flow rate for the given engine speed.

As such, the PCV valve is initially in a more open position during engine starting and the subsequent run-up (e.g. a fully open position when the manifold vacuum is lower and the throttle opening is small). During these conditions, the air flow through the crankcase ventilation tube is substantially higher and can be estimated by the crankcase ventilation tube pressure / flow sensor as a transient increase in vent air flow or a transient increase in ventilation pressure. Thereafter, when engine speed is above a threshold and manifold vacuum is higher, the PCV valve may be in a second, less open, position (e.g., a position with a smaller fixed opening that allows lower flow). For example, in the second position, the flow through the PCV valve can be controlled to a sound-choked hole. During these conditions, the air flow through the crankcase ventilation tube decreases and stabilizes at a steady state, which can also be estimated by the crankcase ventilation tube pressure / flow sensor. If a PCV valve is stuck open, the crankcase ventilation tube air flow may continue to increase in the higher manifold vacuum conditions instead of decreasing and stabilizing at the steady-state value. Likewise, if the PCV valve becomes stuck in the small orifice position during cranking, the crankcase ventilation tube air flow rate may not increase to expected levels during lower manifold vacuum conditions. Consequently, by comparing the characteristic changes in an expected flow / pressure profile of a crankcase ventilation pipe pressure with the actual changes in a crankcase ventilation pipe flow / pressure profile as estimated by a crankcase ventilation pipe pressure / flow sensor, an impairment can be made of the PCV valve can be identified.

Accordingly, at 510 the measured or estimated crankcase ventilation tube pressure profile and / or air flow profile can be compared to the expected crankcase ventilation tube pressure profile and / or air flow profile and it can be determined whether an absolute difference between the profiles is greater than a threshold value . That is, it can be determined whether the expected and actual crankcase ventilation tube pressures or flow rates differ by more than a threshold amount. If not, then at 512 the routine determines that there is no degradation of the PCV valve.

If there is an abnormality, then at 514 it is determined that the PCV valve may be compromised and the routine can proceed to determine the nature of the deterioration based on the estimated crankcase ventilation tube pressure and / or flow rate profiles. Specifically, at 516, it may be determined whether the estimated crankcase ventilation tube pressure or air flow rate is greater than the threshold amount than the expected crankcase ventilation tube pressure (or air flow rate). Alternatively, it can be determined whether an estimated amplitude of a transient drop in crankcase ventilation tube pressure is higher than an expected amplitude (or threshold amplitude). If so, then at 518 It can be determined that due to the PCV valve stuck in the open position, the estimated crankcase ventilation pressure / air flow profile is greater than the expected profile (or the amplitude of the transient drop in crankcase ventilation pressure is greater than an expected amplitude). The control unit can display the same by setting a corresponding diagnosis code.

If the estimated crankcase ventilation pressure or air flow rate is not greater than the expected crankcase ventilation pressure (or air flow rate), then it can be confirmed that the estimated crankcase ventilation pressure or air flow rate is less than the expected crankcase ventilation pressure by more than the threshold amount (or the air flow rate). Alternatively, it may be determined whether an estimated amplitude of a transient drop in crankcase ventilation tube pressure is less than an expected amplitude (or threshold amplitude). After confirmation, 522 determine whether a condition of a crankcase injury has already been determined. As above with reference to FIG 2A to B, a violation of the integrity of the crankcase ventilation system prior to the initiation of the PCV valve diagnostic routine from 5 have been established. As referring to 3 until 4th explained, a violation of the integrity of the crankcase ventilation system and a location of the violation based on characteristics of a temporary drop in crankcase ventilation pressure during engine cranking and a change in crankcase ventilation pressure in steady state relative to a change in manifold air flow in the Permanent condition can be determined while the engine is running.

As such, if there is a violation of the integrity of the crankcase system, there may be a change in one or more of the crankcase ventilation tube pressure and flow rate, both of which have an impact on the output of the crankcase ventilation tube pressure / flow sensor and may have the resulting profile during engine start-up and ramp-up. In addition, the profile is influenced by the position of the crankcase injury. For example, injuries to the crankcase system that occur on the second side of the crankcase ventilation tube (i.e., the side of the crankcase ventilation tube that is coupled to the crankcase) can cause the crankcase ventilation flow rate to decrease due to the fact that the violation causes a short circuit at the expected flow rate can be significantly reduced. Additionally, the crankcase ventilation tube pressure sensor may no longer show negative pressure at high engine air flow rates (compared to the negative pressure shown in the absence of injury at high engine air flow rates). Injuries on the second side of the vent tube that can cause these effects include, for example, separation of the vent tube from the crankcase on the second side, a crankcase oil filler cap coming off, or a crankcase oil level stick being misaligned. As another example, injuries to the crankcase system that occur on the first side of the crankcase ventilation tube (i.e., the side of the crankcase ventilation tube that is coupled to the air intake passage) can cause the crankcase ventilation tube flow rate to be substantially unaffected remains, but the crankcase ventilation tube pressure sensor may no longer show negative pressure at high engine air flow rates (compared to the negative pressure shown in the absence of injury at high engine air flow rates). Injuries on the first side of the vent tube that can cause these effects include, for example, disconnecting the vent tube from the air intake duct on the first side.

Accordingly, if no crankcase damage has previously been detected, the routine at 524 determines that the estimated crankcase ventilation pipe pressure / air flow profile is less than the expected profile (or that the amplitude of the transient decay in crankcase ventilation pipe pressure is less than an expected amplitude) due to the PCV valve in an open Is stuck in a low flow position (e.g. a small orifice position or a closed position). The control unit can display the same by setting a corresponding diagnosis code. In itself, the display of a PCV valve impairment due to the fact that the valve is stuck open (at 518 ) Set diagnostic code of the one used to indicate a PCV valve impairment due to the valve being stuck closed (at 524 ) differentiate the set diagnosis code. If a crankcase damage was previously detected, the control unit can at 526 determine that the PCV valve may be functional and unaffected.

It will be appreciated that in some embodiments, in addition to confirming, at 522 Whether a violation of the crankcase system has been detected, whether an air intake filter has been diagnosed, and if so, a degree of air filter clogging can be included in the PCV valve diagnosis. As in 10 in more detail, if air filter clogging is confirmed, then at 524 the deviation between the expected profile and the estimated profile could be due to the air filter being clogged rather than the PCV valve being stuck in the low flow position. On the basis of the (known) degree of filter clogging in relation to the observed deviation between the estimated and the expected crankcase ventilation tube flow rate profile to distinguish between these conditions. If, for example, the deviation is more than the expected allowance for the degree of filter clogging, a violation of the crankcase system can be determined.

In this manner, PCV valve degradation can be determined based on changes in air flow rate through a crankcase ventilation tube as estimated by a crankcase ventilation tube pressure or flow sensor during engine cranking. Based on deviations of an expected flow profile from an estimated flow profile, a PCV valve impairment due to a stuck open valve can be better distinguished from an impairment due to a stuck closed valve. By performing the PCV valve diagnostic routine after completing a crankcase system diagnostic routine, changes in the crankcase ventilation tube pressure or flow caused by a violation of the crankcase system on either a crankcase side or an air intake duct side of the crankcase ventilation pipe can be included in order to ensure a reliable Enable PCV valve diagnostics. Specifically, changes in crankcase ventilation duct air flow due to a crankcase system damage (e.g. due to a disconnected ventilation duct or an offset oil filler cap) can be better distinguished from those due to an impaired PCV valve.

In another example, in response to the PCV valve being stuck open (or stuck in the high flow position), engine boost may be limited so that the MAP is below the BP. In itself, a stuck open PCV valve will cause crankcase gases and oil mist to be blown into the inlet of the compressor. This leads to the risk of rapid oil consumption, which can be reduced by limiting (or interrupting) charging. In comparison, a stuck closed PCV valve essentially results in a stale crankcase ventilation system. Over a long period of time this leads to engine sludge build-up in the oiled sections of the engine. As a result, no mitigation action may be necessary. Alternatively, in response to the PCV valve being closed (or stuck in the low flow position), an engine speed may be decreased.

It will be seen that while the routine of 5 is depicted as being performed while an engine is being started in alternative embodiments, such as embodiments where the engine is coupled into a hybrid vehicle system or engine start-stop systems where the engine is configured to do so to be selectively shut down in response to idle stop conditions is the routine of 5 can also be executed during key-off conditions (i.e., where a vehicle operator has turned an ignition key to an off position). For example, during a key-off condition, a controller may close an intake throttle and perform a vacuum decay test with the PCV valve in any given position. Thereafter, PCV valve degradation can be determined based on a rate of negative pressure drop from the crankcase ventilation tube.

An exemplary PCV valve diagnosis is given at from 10 illustrated. In detail, the Changes in crankcase ventilation tube air flow rate along the y-axis and changes in manifold vacuum along the x-axis. The diagrams 1002 until 1008 depict exemplary changes in vent tube flow rate versus manifold vacuum used to diagnose a PCV valve.

The diagram 1002 provides a first map of an expected change in crankcase ventilation tube air flow rate during engine cranking and ramp-up. As previously detailed, during engine cranking, when the manifold vacuum is low (and the throttle opening is small), the PCV valve can be in an open position, causing a large amount of air, from an intake air filter, to pass through the crankcase ventilation duct , via the crankcase, into the intake manifold. As a result, at low manifold vacuum levels (eg, at or around 13 kPa), there is a significantly high rate of air flow through the crankcase ventilation tube. Thereafter, as the engine progresses from cranking to ramp-up, a throttle opening can increase, a PCV valve opening can decrease (e.g. to a fixed position with a smaller opening or a position with a low flow rate), a manifold vacuum can increase (e.g. above 13 kPa) , and air flow into and through the crankcase ventilation tube may decrease causing a decrease and eventually stabilization of the crankcase ventilation tube air flow rate.

The diagram 1004 Figure 12 shows a second mapping of an estimated change in crankcase ventilation tube air flow rate during engine cranking and ramp-up in the presence of a stuck open PCV valve. Here, as the engine progresses from cranking to ramp-up, the PCV valve opening does not decrease, as would be expected, due to the PCV valve stuck open. As a result, as manifold vacuum increases, air flow into and through the crankcase ventilation tube may continue to increase, causing the estimated crankcase ventilation tube air flow rate and profile (Graph 1004 ) are higher than the expected air flow rate and the profile (diagram 1002 ).

The diagram 1006 Figure 13 shows a third map of an estimated change in crankcase ventilation tube air flow rate during engine cranking and ramp-up in the presence of a stuck open PCV valve. Here, the PCV valve may not be able to open to the fully open position during engine cranking, which causes a considerably smaller amount of air from the intake air filter, through the crankcase ventilation tube, via the crankcase, into the intake manifold is directed. As a result, at low manifold vacuum levels, a significantly lower rate of air flow through the crankcase ventilation tube can be seen, causing the estimated crankcase ventilation tube air flow rate and profile (Diagram 1006 ) are lower than the expected air flow rate and the profile (diagram 1002 ).

The diagram 1008 Figure 4 shows a fourth illustration of an estimated change in crankcase ventilation tube air flow rate during engine cranking and ramp-up in the presence of a functioning PCV valve and an air filter that is completely clogged. As with diagram 1006 during engine starting, even though the PCV valve is open, air flow from the intake air filter, through the crankcase ventilation pipe, via the crankcase, into the intake manifold may be reduced due to the clogged air filter. As a result, at low manifold vacuum levels, a significantly lower rate of air flow through the crankcase ventilation tube can be seen, causing the estimated crankcase ventilation tube air flow rate and profile (Diagram 1006 ) are lower than the expected air flow rate and the profile (diagram 1002 ).

In one example, the diagram is 1002 observe the diagram if the PCV valve is not affected 1004 Observe if the PCV valve is stuck in a low throttling position is the diagram 1006 watch if the PCV valve is stuck in a high restriction position and is the diagram 1008 watch if the air filter is clogged or stuck closed

It will be seen that while the example of 10 illustrates determining PCV valve degradation based on deviations in an estimated vent tube air flow rate profile from an expected air flow rate profile, in an alternative example the same can be determined (or illustrated) by deviations in an estimated vent tube vacuum profile from an expected vacuum profile. In this way, an existing sensor used to monitor the crankcase ventilation system can advantageously be used to reliably diagnose a PCV valve.

Now 6th facing, is an exemplary procedure 600 for indicating deterioration of an intake air filter based on a crankcase ventilation pressure estimated by a pressure sensor in the crankcase ventilation tube. In itself, the routine of 6th as part of the routine of 2A through B.

at 602 the routine includes confirming whether the manifold air flow rate is less than a first threshold. By confirming that the manifold air flow is less than the first threshold, it can be confirmed that a sensor compensation is being calculated during low engine flow conditions (such as when there is no engine flow) so as to reduce noise interference that occurs at the calculation from the motor flow. Next, at 604, crankcase ventilation pressure during low manifold air flow conditions may be estimated by a pressure sensor located in the crankcase ventilation. The pressure sensor in the crankcase ventilation tube can be, for example, an absolute pressure sensor or a relative pressure sensor. In embodiments in which the pressure sensor is an absolute pressure sensor, it may or may not be coupled to an air pressure sensor. In embodiments in which the pressure sensor is a Is a relative sensor, an absolute air pressure sensor (e.g. the BP sensor 57 from 1 ) be coupled to it (e.g. additionally present outside of the filtered volume) or used in conjunction.

at 606 the routine includes calculating a sensor offset. Specifically, the algorithm used will zero the gauge pressure sensor during low engine flows or learn a sensor offset based on the barometric pressure reading from the BP sensor during low engine flow conditions. In this way, the control unit learns or inferences the air pressure from the crankcase ventilation tube pressure sensor and can either use the output of the crankcase ventilation tube pressure sensor itself as air pressure at a low engine flow rate or can use the output to establish a common and calibrated reference to an air pressure which is separate is measured. In one example, the air pressure may be separate from a dedicated air pressure sensor coupled to the intake duct (e.g., upstream of the air filter), or from a compressor inlet pressure (CIP) sensor located in the inlet upstream of the compressor and downstream of the Air filter is arranged to be learned. However, using the existing crankcase ventilation pressure sensor to estimate BP reduces the need for a BP sensor or a CIP sensor.

In one example, the pressure sensor in the crankcase ventilation tube is a first pressure sensor and the offset is determined based on a second pressure sensor (e.g., a BP sensor) coupled downstream of the air filter and upstream of the compressor. In particular, the offset may be based on the output of the first pressure sensor relative to the output of the second pressure sensor during low manifold air flow conditions. For example, if the first pressure sensor is an absolute pressure sensor without a BP sensor, the output of the first pressure sensor can be used to infer the BP. As another example, if the first pressure sensor is an absolute pressure sensor with a BP sensor, the difference between the outputs of the first pressure sensor and the coupled BP sensor can be used to infer the BP and learn a sensor offset . As yet another example, if the first pressure sensor is a relative pressure sensor, the difference of the first pressure sensor from a zero reading can be used to infer the BP and calculate a sensor offset.

The calculated offset can then be stored in the memory of the control unit as a reference pressure. The stored offset can then be retrieved and applied during subsequent higher engine flow conditions to identify air filter clogging, as detailed below.

Next can be at 608 determine whether the engine air flow (or some other signal associated with the engine air flow rate) is greater than a second threshold value. By confirming that the engine air flow is higher than the second threshold, it can be determined that air filter clogging is estimated during higher engine flow conditions when the effect of air filter clogging on the crankcase ventilation pipe pressure is greater, so as to improve the detection accuracy . If engine air flow is not greater than the second threshold, the routine may wait until desired engine air flow levels are reached in order to perform air filter clogging diagnosis. at 610 For example, after confirming that the manifold air flow levels are higher than the second threshold, it can be confirmed that the sensor offset has been updated. This may include confirming that the sensor offset learned during the lower engine flow conditions that immediately preceded the higher engine flow conditions has been stored in the controller (e.g., a look-up table with the most recently learned sensor Offset has been updated).

at 612 After confirming that the offset has been updated, the sensor output (s) can be adjusted based on the updated offset. This includes adjusting the output of the crankcase ventilation tube pressure sensor with the updated offset. at 614 it can be determined whether the deviation between the adjusted sensor output and an estimated / inferred BP is greater than a threshold value. In one example, the deviation may be based on the difference between the sensors. In another example, the deviation is due to a ratio between the sensor outputs. If the difference is not greater than the threshold amount, then it can be determined at 616 that the air filter is clean and not clogged. In comparison, if the difference is greater than the threshold amount, then at 618 air filter clogging may be indicated. A degree of air filter clogging can be determined based on the difference between the adjusted sensor output and the BP (e.g., relative to the threshold).

wobei der Verstopfungsfaktor unter Bezugnahme auf Standardbedingungen (STP) festgestellt wird.In an alternative example, a deviation between the indication of the crankcase ventilation tube pressure at high air flow (which is substantially equal to the CIP) and the estimated reference pressure at low air flow may be calculated. A reference air filter differential pressure can then be obtained from a look-up table. The control unit can then compensate for the reference air filter differential pressure for actual conditions and calculate a clogging factor from the ratio of Delta-CIP to the compensated reference differential pressure. That is, the controller can calculate an instantaneous air filter clogging factor based on a ratio of the difference between the estimated crankcase ventilation tube pressures during high and low air flow conditions relative to a reference air filter decrease, with a correction factor for non-standard temperature and pressure ( STP). In one example, the STP conditions include 103 kPa and 100 ° F (= 37.8 ° C). As an example, the controller can estimate the clogging factor using the following equation: $$\begin{array}{l}\mathrm{A.}uGenblicklicHerVerstOpfunGsfaktOr=\\ \frac{\mathrm{B.}\mathrm{P.}-Offset-\mathrm{C.}V\mathrm{P.}-\mathrm{S.}ensOranzeiGe}{\mathrm{F.}\left(\mathrm{L.}uftdurcHflussbei\mathrm{B.}edinGunGen\right)\ast \mathrm{F.}\left(\mathrm{B.}\mathrm{P.},\mathrm{I.}\mathrm{A.}T\right)}{}^{\ast \mathrm{F.}\left(\mathrm{L.}uftdurcHfluss\right)}\end{array}$$

the clogging factor being determined with reference to standard conditions (STP).

at 620 the controller can set a diagnostic code to indicate an air filter clog. As such, the diagnostic code used to indicate air filter clogging may be different from a diagnostic code used to indicate violation / degradation of the crankcase ventilation system. The controller can also illuminate a MIL light to advise the vehicle operator to service the air filter. The controller can also limit engine output to reduce compressor over-rev and overheating that can be caused by the clogged air filter.

In this way, by indicating air filter degradation based on crankcase ventilation pressure, both crankcase system health and air filter clogging can be monitored using a single set of sensors already present in the crankcase ventilation.

Exemplary air filter clogging diagnosis is provided in from 9 illustrated. In detail, the Changes in crankcase ventilation tube pressure along the y-axis and changes in manifold air flow along the x-axis. The diagrams 902 until 906 depict exemplary changes in vent tube pressure versus manifold air flow that are used to indicate a condition of an intake air filter.

During low engine air flow conditions, such as before the manifold air flow is at a first threshold AF1, an offset for the crankcase ventilation pressure sensor may be learned. For example, if the crankcase ventilation pressure sensor is an absolute pressure sensor, the air pressure may be inferred based on the output of the crankcase ventilation pressure sensor or based on an offset between the ventilation tube pressure sensor and a coupled BP sensor. With reference to the P1 (which extends across the figure as a dashed line) reflects the inferred reference BP when the crankcase ventilation tube pressure sensor is in absolute pressure sensor. In an alternative example, the crankcase ventilation tube pressure sensor can be a relative pressure sensor, wherein an offset of the pressure sensor reading from a zero reading is learned such that P1 on the reflects a balanced reference zero pressure.

No offset may be learned or applied during mean manifold air flow conditions, that is, when the manifold air flow is higher than the first threshold AF1 but lower than a second threshold AF2. Thereafter, when high manifold air flow conditions are reached, such as when the manifold air flow is higher than the second threshold AF2, the learned offset can be applied to determine an air filter clogging factor.

The diagram 902 shows deviations in crankcase ventilation tube pressure from reference P1 , as estimated by a crankcase ventilation pressure sensor, relative to changes in manifold air flow in the absence of an air filter clog (ie, a clean air filter). The diagram 904 shows a corresponding deviation in crankcase ventilation pressure from P1, relative to manifold air flow, when the air filter is partially clogged. The diagram 906 shows changes in crankcase ventilation pressure versus manifold air flow when the air filter is dirty and substantially clogged. Like by comparing the diagrams 902 until 906 As can be seen, as the clogging factor of the air filter increases, there will be a deviation in pressure from the reference P1 to. A controller can determine the degree of filter clogging based on the degree of deviation. In this way, an existing sensor used to monitor the crankcase ventilation system can advantageously be used to reliably diagnose an air filter blockage as well.

In this way, by placing a pressure sensor within a crankcase ventilation tube, changes in pressure and air flow through the ventilation tube can be monitored while the sensor is housed in an inexpensive manner. By correlating the estimated changes in ventilation tube pressure in the crankcase with expected values, crankcase system health, air filter degradation, and PCV valve degradation can be reliably indicated. By relying on properties of crankcase ventilation pressure and flow data during engine cranking and running, injuries in the crankcase ventilation system that are on one side of the ventilation duct that is coupled to an air intake duct can be better distinguished from those that are occur on one side of the vent pipe that is coupled to a crankcase. By making adjustments to a throttle and / or a PCV valve to increase intake manifold vacuum during engine cranking, crankcase injury detection accuracy can be increased. By also using the crankcase ventilation system pressure sensor to identify air filter clogging as well as PCV valve deterioration, the need for additional sensors and valves to monitor air filter deterioration and PCV valve deterioration can be reduced, providing advantages of cost and complexity reduction without the Decrease the accuracy of the impairment detection. In addition, an engine crankcase ventilation system can remain active during diagnostic procedures.

It will be recognized that the configurations and methods disclosed herein are exemplary in nature and that these specific embodiments are not to be considered in a limiting sense because numerous variations are possible. For example, the above technology can be applied to V6, R4, R6, V12, Boxer-4 and other types of engines. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

Claims (20)

A method for an engine comprising: indicating degradation of the crankcase ventilation system based on characteristics of a transient drop in crankcase ventilation pressure during engine cranking, wherein an end of the crankcase ventilation (74) upstream of a compressor (50) is mechanically connected to an intake passage (13) of the engine connected is. Procedure according to Claim 1 , wherein includes during engine cranking prior to a first combustion event from a standstill. Procedure according to Claim 2 , wherein based on properties of a transient fall includes based on an amplitude of the transient fall. Procedure according to Claim 3 wherein the indicating includes indicating degradation of the crankcase ventilation system based on the amplitude of the transient decay being less than a threshold amount. Procedure according to Claim 4 wherein the threshold level is based on the intake manifold vacuum during engine cranking, the threshold level increasing as the expected flow through the PCV valve (78) changes. Procedure according to Claim 5 wherein indicating a degradation of the crankcase ventilation system includes indicating that a crankcase ventilation tube (74) is disconnected. Procedure according to Claim 6 wherein the crankcase ventilation tube pressure is estimated by one of a pressure sensor (77), a flow sensor, and a venturi tube (75) in the crankcase ventilation tube (74). Procedure according to Claim 7 further comprising, after an engine speed reaches a threshold speed, indicating a deterioration in the crankcase ventilation system based on a change in crankcase ventilation pressure relative to a change in manifold air flow through the engine. Procedure according to Claim 8 , wherein the indicating means indicating that for a period of time while the engine speed is at or above a threshold speed, the crankcase ventilation tube (74) is disconnected based on that a decrease in crankcase ventilation pressure is not proportional to an increase in Manifold air flow is includes. Procedure according to Claim 6 wherein another, opposite end of the crankcase ventilation tube (74) is mechanically coupled to an engine crankcase via an oil separator (81). Procedure according to Claim 1 wherein the indicating includes setting a diagnostic code, the method further comprising, in response to the indication, limiting an engine speed and load. A method for an engine comprising: indicating disconnection of a crankcase ventilation tube (74) from an engine crankcase ventilation system based on a temporary change in air flow through the crankcase ventilation tube (74) during engine cranking, with one end of the crankcase ventilation tube (74) upstream of a compressor (50) is mechanically connected to an intake duct (13) of the engine. Procedure according to Claim 12 wherein the transient change in air flow is estimated by a flow sensor (77) coupled to the crankcase ventilation tube (74), the flow sensor (77) including a venturi tube (75). Procedure according to Claim 12 wherein the transient change in air flow is due to a transient drop in crankcase ventilation tube pressure as assessed by a pressure sensor (77) coupled to the crankcase ventilation tube (74). Procedure according to Claim 12 , including during engine cranking during an engine start from rest when the manifold air flow is less than a threshold. Procedure according to Claim 15 and, after the manifold air flow is at the threshold, indicating a disconnection of the crankcase ventilation tube (74) based on a rate of decrease in steady-state crankcase ventilation pressure relative to a rate of increase in steady-state manifold air flow, during the engine is running above idle speed. Procedure according to Claim 16 wherein the indicating includes indicating disconnection of the crankcase ventilation tube (74) based on the rate of decrease in steady-state crankcase ventilation pressure is not proportional to the rate of increase in steady-state manifold air flow. An engine crankcase ventilation system comprising: an engine including an intake passage (13) and a crankcase (26), a crankcase ventilation pipe (74) mechanically connected to the intake passage (13) upstream of a compressor (50) , the pipe (74) also being mechanically connected to the crankcase (26) via an oil separator (81), the ventilation pipe (74) being arranged outside the engine, a sensor (77) coupled into the crankcase ventilation pipe (74) for estimating a ventilation pipe pressure, a sensor for determining the manifold air flow in the area of an intake manifold (42) and a control system (12) having computer readable instructions for, during an engine start, indicating a degradation of the crankcase ventilation system based on both a temporary drop in vent pipe pressure being less than a threshold amplitude during engine cranking when the manifold air flow rate is below a As well as that a change in vent tube vacuum is less than a change in manifold air flow during engine operation when the manifold air flow is above the threshold. System according to Claim 18 wherein indicating a degradation of the crankcase ventilation system includes setting a diagnostic code to indicate that the crankcase ventilation tube (74) is disconnected from at least one of the intake passage (13) and the crankcase (26). System according to Claim 19 wherein the sensor (77) is one of a pressure sensor, a flow sensor, and a venturi tube (75), the system further comprising an air pressure sensor (57) in the intake duct (13) for estimating an air pressure and wherein the vent tube pressure is estimated based on an output of the sensor (77) in the crankcase ventilation tube (74), the output being adjusted with an offset based on the estimated air pressure.

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